The degree of certainty in one's level of competency is inversely proportional to the actual level.
1. The hopelessly incompetent are absolutely certain of their abilities.
2. The competent always have sensible doubts, precisely for the reason that they can realistically assess the situation.
3. The incompetent never realize they are incompetent, precisely for the reason that they lack the competence necessary to discern the difference.
4. The work of the incompetent tends to be superficial and bombastic. By extension of Corollary 3, they are completely unaware of this and usually regard their work as profound and important. The converse also tends to be true: those who regard their work as profound and important usually have an unrealistic appreciation of their abilities (or lack thereof).
5. The incompetent tend to hire people like themselves, since, for obvious reasons, they do not find their own kind threatening. Moreover, they usually confuse the sensible doubts of the competent (see Corollary 2) with a bad attitude, and the overconfidence of the incompetent (see Corollary 4) with great promise.
6. The competent are only tolerated because they are needed to perform all the necessary tasks that the incompetent regard as beneath them, but which are, in reality, beyond their ability.
7. The truly gifted don't even think about any of this. They just do their thing. The converse, however, is far from true.